Efficient image scaling for scan rate conversion

Abstract

The present invention is a method and apparatus for converting scan rates of image data in a memory. A buffer stores a source image data. A scaling filter is coupled to the buffer to scale the source image data.

What is claimed is:  
     
       1. A method comprising: 
       storing a source image data in a buffer, the storing comprises transferring a patch of the source image data from a memory to the buffer; and  
       scaling the source image data using a scaling filter, the scaling comprises down-scaling the source image data using a patch-based filter, the down scaling comprising:  
       band-limiting the source image data in the patch by an FIR filter, and  
       re-sampling the band-limited patch of the source image data by an interpolator to generate a sub-sampled patch, the sub-sampled patch corresponding to a down-scaled image data.  
     
     
       2. The method of claim  1  wherein scaling further comprises: 
       horizontally up-scaling the source image data using an in-line horizontal filter.  
     
     
       3. The method of claim  2  wherein the in-line horizontal filter is a multi-tap FIR filter having N taps. 
     
     
       4. The method of claim  3  wherein N=4. 
     
     
       5. The method of claim  1  wherein scaling further comprises: 
       vertically up-scaling the source image using an in-line vertical filter.  
     
     
       6. The method of claim  5  wherein the in-line vertical filter is a multi-tap interpolator having N taps. 
     
     
       7. The method of claim  6  wherein N is one of 2 and 3. 
     
     
       8. An apparatus comprising: 
       a buffer to store a source image data, the buffer storing a patch of the source image data from a memory; and  
       a scaling filter coupled to the buffer to scale the source image data, the scaling filter comprising a patch-based down-scaling filter coupled to the buffer to down-scale the source image data, the down scaling filter comprising:  
       a finite impulse response (FIR) filter coupled to the buffer to band-limit the source image data in the patch, and  
       an interpolator coupled to the FIR filter to re-sample the band-limited patch of the source image data, the interpolator generating a sub-sampled patch, the sub-sampled patch corresponding to a down-scaled image data.  
     
     
       9. The apparatus of claim  8  wherein the scaling filter further comprises: 
       an in-line horizontal filter coupled to the buffer to horizontally up-scaling the source image data.  
     
     
       10. The apparatus of claim  9  wherein the in-line horizontal filter is a multi-tap FIR filter having N taps. 
     
     
       11. The apparatus of claim  10  wherein N=4. 
     
     
       12. The apparatus of claim  8  wherein the scaling filter further comprises: 
       an in-line vertical filter coupled to the buffer to vertically up-scale the source image.  
     
     
       13. The apparatus of claim  12  wherein the in-line vertical filter is a multi-tap interpolator having N taps. 
     
     
       14. The apparatus of claim  13  wherein N is one of 2 and 3. 
     
     
       15. A system comprising: 
       a decoder to provide a source image data; and  
       a filtering and format conversion unit (FFCU) coupled to the decoder to convert scan rates of image data in a memory, the FFCU comprising:  
       a buffer to store the source image data, the buffer storing a patch of the source image data from a memory, and  
       a scaling filter coupled to the buffer to scale the source image data, the scaling filter comprising a patch-based down-scaling filter coupled to the buffer to down-scale the source image data, the down scaling filter comprising:  
       a finite impulse response (FIR) filter coupled to the buffer to band-limit the source image data in the patch, and  
       an interpolator coupled to the FIR filter to re-sample the band-limited patch of the source image data, the interpolator generating a sub-sampled patch, the sub-sampled patch corresponding to a down-scaled image data.  
     
     
       16. The system of claim  15  wherein the scaling filter further comprises: 
       an in-line horizontal filter coupled to the buffer to horizontally up-scaling the source image data.  
     
     
       17. The system of claim  16  wherein the in-line horizontal filter is a multi-tap FIR filter having N taps. 
     
     
       18. The system of claim  17  wherein N=4. 
     
     
       19. The system of claim  15  wherein the scaling filter further comprises: 
       an in-line vertical filter coupled to the buffer to vertically up-scale the source image.  
     
     
       20. The system of claim  19  wherein the in-line vertical filter is a multi-tap interpolator having N taps. 
     
     
       21. The system of claim  20  wherein N is one of 2 and 3.